Domestic appliance control probe



Aug. 1, 1967 J. 1.. MILLER 3,333,345

DOMESTIC APPLIANCE CONTROL PROBE Filed May 20, 1965 4 Sheets-Sheet 1 v mg l8 Fig 2 IO l2 J INVENTOR. James L. Miller BY Qc. g

His Afforney Aug. 1, 1967 J. MILLER DOMESTIC APPLIANCE CONTROL PROBE 4 Sheets-Sheet 2 Filed May 20, 1965 m 5k mm w: v1 0 3 m: f 7 m0. N: O: a 02 mg @Q S. we 5 Mg mm mm om I\ ON INVENTOR. James L. Mil/er BY )4 gm H is A homey 8- ,l967 MILLE 3,333,345

DOMESTIC APPLIANCE CONTROL PROBE Filed May 20, 1965 4 Sheets-Sheet 5 us r I30 4 @E Ml I20 I30, 3 I '20 w w INVENTOR. I44 H8 Fig 5 mes L.M///er I26 BY His Attorney 1967 J. L. MILLER 3,333,345

DOMESTIC APPLIANCE CONTROL PROBE Filed May 20, 1965 4 Sheets-Sheet 4 s4 22 g 1 q H A H 'H 303/ rmw 268 240 242 I INVENTOR. Fly. 6 James L. Mil/er BY 65m His Afforney United States Patent ABSTRACT OF THE DISCLOSURE In preferred form, a clothes dryer control probe secured at the center of a rear wall of a tumbling drum and including an interrupted current path located interiorly of the drum to be randomly bridged by articles tumbling through the drum for conditioning control circuit means and further including a conically shaped base for directing tumbled articles from the vicinity of the rear wall and across the current path for wiping foreign matter from the probe.

This invention relates to clothes dryer units and more particularly to clothes dryer units having dryness control systems including sensor means that control the operation of the dryer in accordance with the dampness of articles being processed.

One problem in controlling domestic clothes dryers is the need to closely regulate the drying action thereof in accordance with the type of articles being processed within the dryer. Such controlled dryer units preferably should be capable of establishing the final degree of clothes dryness through a relatively substantial range whereby various types of natural and synthetic fabrics can be finally dried to a particular state that either results in a small percentage of retained moisture that improves the fabric for ironing or to a final dryness state having a slight moisture therein that prevents the processed articles from becoming unduly wrinkled as in the case in certain synthetic fabrics when they are dried to a bone dry state.

While various dryer control systems have been proposed to produce a controlled termination point resulting in a predetermined retained moisture level, such control systems typically lack sufficient sensitivity or control range to adequately handle a wide range of fabrics.

Accordingly, ,an object of the present invention is to improve clothes dryers of the type wherein drying termination is regulated by a control unit including a chargeable capacitor by the provision of a sensor unit located interiorly of the drum and operative to selectively contact articles in the drum to randomly complete a grounding circuit associated with the chargeable capacitor unit in a manner to increase the sensitivity of regulation of the unit.

Still another object of the present invention is to improve domestic clothes dryer operation by regulating the termination of drying therein by control means including an improved sensor unit having an interrupted current path therethrough arranged interiorly of a tumbling drum adjacent the rear wall thereof at a central region thereon so that wet articles being tumbled occasionally will complete the interrupted current path through the sensor for conditioning a capacitive circuit in a dryness control unit of the control means to closely control the final termination of drying.

Yet another object of the present invention is to improve domestic dryers by the provision of a dryness control unit having a sensing probe including an interrupted current path therethrough selectively completed by contacting articles being tumbled interiorly of a drum wherein the probe is located on the rear wall of the tumbling carried by the front wall 16 of the dryer cabinet. More 3,333,345 Patented Aug. 1, 1967 drum and includes a surface configuration to prevent tumbled articles from becoming tangled on the probe.

Yet another object of the present invention is to provide an improved moisture sensing probe for association with an electronic control system for terminating drying in a domestic dryer including a comically-shaped base portion adapted to be secured to the end wall of a tumbling drum and having a nose portion on the small diameter end portion of the comically-shaped base portion located interiorly of the drum and including an interrupted conductive current path therethrough selectively completed by contacting clothes tumbled by the drum to condition the associated electronic drying control system for terminating drying action in the drum.

Still another object of the present invention is to provide a sensing probe having a conically-shaped base portion adapted to be connected to the rear wall of a tumbling drum that includes a nose member on the small diameter end thereof disposed interiorly of the drum wherein the nose member includes a plurality of spaced and electrically insulated conductor members thereon forming an interrupted current path through said nose member completed by contact of the nose member with articles being tumbled in the drum; and to provide such a sensing probe wherein the nose member has a stepped outer configuration to prevent tangling oftumbled clothes thereon.

Still another object of the present invention is to improve domestic dryer units by the provision of an article contacting sensing probe located interiorly of the drum on the rear wall thereof including conductive members thereon providing an interrupted current path thereon completed by engagement of the probe with articles tumbled in the drum and further including first and second terminal members electrically connected to the conductor members for directing current flow therethrough exteriorly of the drum wherein one of the terminal members is electrically connected to ground. and the other of the terminal members is electrically connected to a fixed point contact located on the outer casing of the dryer unit.

Further objects and advantages of the present invention will be apparent from the following description, refer ence being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a vertical, sectional view of a clothes dryer including the present invention;

FIGURE 2 is a fragmentary, front elevational view of the control panel of the dryer of FIGURE 1;

FIGURE 3 is an enlarged, fragmentary view showing the sensing probe of the invention partially in section and partially in elevation;

FIGURE 4 is an end elevational view of the sensing probe of FIGURE 3;

FIGURE 5 is an enlarged view in vertical section taken along the line 5--5 of FIGURE 4; and

FIGURE 6 is a schematic wiring diagram for controlling a clothes dryer with the sensing probe of the present invention. A

Referring now to FIGURE 1 of the drawings, a clothes dryer 10 is shown having an outer casing with a top wall 12, a rear wall 14, a front wall 16, side Walls 17 and a control housing 18. Disposed between the top wall 12 and a bottom wall 19 of the casing is a vertical drum support bulkhead 20 supportingly receiving a centrally located universal support bearing 22 in which a drum shaft 24 is rotatably mounted. A tumbling drum 26 is supported by and fixed to the shaft 24 at one end thereof and is supported at its other end on a port plate 28 particularly, a front wall of the tumbling drum includes an axially directed outwardly turned cylindrical flange 32 thereon which overlies an inturned flange 34 on the port plate 28. Sealing material such as felt 36 may be interposed along with a pair of bearing support blocks (not shown) between the flanges 32, 34 for rotatably supporting the front end of the tumbling drum 26.

The rear wall 40 of the tumbling drum is perforated, as at 42, to communicate the interior space 44 of the tumbling drum 26 with a heating chamber 46 formed adjacent the outer surface of the rear wall 40 by an annular sealing member 48 fixed to the bulkhead 20 and having a flexible end thereof slidably engaging the outer surface of wall 40.

The chamber 46 communicates through an opening 50 inthe rear bulkhead 20 with an inlet chamber 52 and has a main heater 54 disposed therein. The rear wall 14 has an opening 56 therein to permit a series flow of air from exteriorly of the outer casing into the interior 44 of the tumbling drum. The series flow through the drum interior 44 leaves the front of the tumbling drum through the port plate 28 and passes through a front duct 60 by means of a passageway 62 formed between a front door closure 64 and the port plate 28. A removable lint screen 66 can be interposed in the air flow path within the front duct 60.

Beneath the tumbling drum 26 and within the dryer cabinet, a conventional blower 68 is disposed which has an inlet 70 thereto connected by means of a flexible conduit 72 to an outlet 74 from the front duct 60. An outlet 76 from the blower 68 communicates by means of a second flexible conduit 78 to exteriorly of the outer casing of the dryer 10. The blower 68 and tumbling drum 26 are both operated by a conventional motor 80, the blower impeller by means of a shaft 82 and the tumbling drum 26 through a belt and pulley system shown generally at 84.

By virtue of the above-illustrated arrangement, when the blower 68 and heater unit 54 are energized, air will be drawn from exteriorly of the cabinet through the opening 56 in the rear wall 14 thereof thence through the openings 50 into the heating chamber 46. Air passes through the perforations 42 in the rear wall 40 through the interior 44 of the drum thence through the wall port plate 28 and the door passageway 62 into the front duct 60. The heated moist exhaust air is drawn across the filter 66 and through the conduit 72 by the blower 68 to be discharged through the outlet 76 to exteriorly of the dryer through flexible conduit 78.

In accordance with certain principles of the present invention, as heated air is circulated through the tumbling drum 44, damp clothes being tumbled therein by rotation of the drum will randomly contact a drum sensor unit 86 located on the rear wall 40 of the drum 26 colinearly of the rear drum support shaft 24, more particularly, as best seen in FIGURES 3 and 4, the sensor 86 includes a comically-shaped base portion 88 having rearwardly directed tubular projections 90, 92, 94 thereon located at spaced circumferential points around the base portion 88. Each of the tubular projections 90, 92, 94 are connected to the rear wall 40 of the tumbling drum at an outwardly bulged portion 96 therein by suitable fastening means such as screw elements 98. The small diameter end of the comically-shaped base portion 88 is spaced inwardly of the rear wall 40 closely adjacent thereto so as to locate a moisture responsive nose portion 100 of the sensor 86 in an out-of-the-way location within the drum interior 44 and preferably colinearly of the support shaft 24 of the drum 26. The nose portion 100 includes a plurality of alternating metallic and insulating discs with alternate ones of the metal discs being grounded and ungrounded metal discs being connectible to dryer control means located exteriorly of the tumbling drum 26.

More particula1ly, as best seen in FIGURE 5, the nose portion includes a first plurality of alternating metal and insulating discs 102 having a diameter substantially equal to the diameter of the small end of the conicallyshaped portion 86. Located in axial abutment with the disc group 102 is a small diameter disc group 104 extending still further into the tumbling drum interior 44. In axial abutment with the disc group 104 is a still smaller disc group 106 located still further within the drum interior 44. In the illustrated embodiment, the disc groups 102, 104, 106 are held against the small diameter end of the conically-shaped portion 86 by an end cap 108 of a suitable electrical insulating material that is held against the innermost end of the disc group 106 by a first stud 110 secured to the base portion 88 by a nut 112 and a like second stud 114 secured to the base 88 by a nut 116. With reference to the disc group 102, it is illustrated as including a first plurality of spaced thinsectioned discs 118 of a suitable electrical insulating material having a good electrical insulating breakdown characteristic such as Mylar or Teflon. To obtain the desired breakdown characteristics, the insulating material preferably should have a resistance when cold in the order of 200,000 megohms and should retain a very high resistance in the order of 300 megohms under operating conditions. Sandwiched between each of the insulating discs 118 are alternately located electrical conductive discs 120 that each has a tubular portion 122 thereon through which is received the stud element 110 to be located in good electrical contact therewith. The discs 120 each also includes a larger diameter opening 124 through which is directed the stud element 114 located in spaced relationship with the discs 120. The group 102 also includes a conductive disc 126 located between the discs 120 and yet another conductive disc 128 located on the end of the group 102 in axial abutment with the inner end of the group 104. The conductive discs 126, 128 each has a tubular portion 130 thereon through which is directed the stud element 114 that is in engagement therewith to be in good electrical contact therewith. The discs 126, 128 each also includes a large diameter opening 132 through which is directed the stud element 110 in spaced relationship therewith. The conductive discs 120, 126, 128 are each electrically insulated from the other by one of the insulating discs 118 and each of the insulating discs 118 has a slightly greater outer diameter than the adjacent conductive discs in the group 102 for purposes to be discussed.

The disc group 104 has the same number of discs as the group 102 arranged in an identical fashion except that the outer diameters of the conductive discs are less than that of the conductive discs in the first group 102. As was the case in the first group 102, the insulating discs in the group 104 are of a slightly greater diameter than the conductive discs in the group 104. The group 106 includes a similar number of discs as the groups 102, 104 which are arranged in a like fashion as the discs in the groups 102, 104 except that the discs of group 106 have a still smaller outer diameter than the discs of the group 104.

In the illustrated arrangement the electrically conductive discs contacting the stud element 110 are electrically connected therethrough to an S-shaped terminal 134 that has the outer end thereof electrically connected by the screw 98 through a reinforcing plate 136 on the outer surface of the bulged portion 96 in the drum wall 40. The.

plate 136 is electrically and mechanically connected to the drum shaft 24 by a flange member 138 and the shaft 24 and flange member 138 are electrically conductive for directing current through a drum ground member 140 having one end thereof fixedly secured at 142 to the bulkhead 20 and the opposite end thereof slidably contacting the outer surface of the universal support bearing 22, as best seen in FIGURE 3.

The conductive discs electrically connected to the stud element- 114 are electrically connected to an S-shaped terminal 144 which has the outer end thereof secured to a rearwardly directed portion 146 of the base 88 by a fastener 148. The fastener 148 also secures a transversely directed flexible spring conductor 150 to the base portion 146 so that the terminus end thereof overlies the axis of the drum shaft 24. The shaft 24 has an axial opening 152 therethrough through which is directed an insulated probe 154 having an end collar 156 thereon overlying the end of the shaft 24 and located within the interior of the sensor unit 86. The probe has a suitable electrical conductor 157 directed interiorly thereof through its length which connects with an exposed fixed electrical contact 160 that is in electrical contact with the end of the spring conductor 154). The conductor 157 is electrically connected to an insulated conductor rod 158 that fixes the conductor 157 against rotation with respect to the shaft 24 for electrically connecting the conductive discs on the nose portion 100 exteriorly of the drum 26 during rotation thereof through a drying cycle of operation.

In the illustrated embodiment of the present invention, the conductor rod 158 from the sensor 86 is electrically associated with a control unit 164 for controlling the operation of the dryer unit. In the illustrated embodiment of the invention the control unit 164 is seen to include a dryer cycle control knob 166 and a plurality of selector buttons located adjacent the knob 166 on the control housing 18 including a start button 168, a no-heat button 170, a delicate and sprinkle cycle button 172, a regular heavy cycle button 174, a wash and wear cycle button 176 and a cancel button 178. The cycle knob 166 and selector buttons 168 through 178 are associated with a suitable electrical control system, illustrated in FIGURE 6, to open and close contacts therein.

In the circuit of FIGURE 6, a conventional power supply is shown including wires L L and a wire N. The wire L is connected to a power supply conductor 180 connected across a door switch 182 that is closed when the door closure 64 of the dryer is closed. The switch 182 is connected through a conductor 184 and a bank of control switches 185 for supplying power to a heater circuit 186, a motor circuit 188 and a dampness control circuit 190. The switch bank 185 includes a cancel switch 192 connecting the conductor 184 to a conductor 194 which, in turn, is connected through a start switch 196 that is electrically connected by a conductor 198 to the control circuit 190. When any one of the dryer selector buttons 172, 174, 176 are depressed for clothes selection, a switch 200 in the switch bank 185 is closed to connect a conductor 202 from conductor 180 with the heater circuit 186. The circuit 186 includes a conductor 204, a relay controlled switch 206, a conductor 208, a bimetallic element 210 of a control thermostat 212 including a heater element 214. The heater circuit 186 further includes a safety thermostat 216 serially connected with the bi-metallic element 210. The safety thermostat 216 is serially connected by a conductor 218 to the main heater element 54 of FIGURE 1 which is connected through a motor speed responsive switch 220 by a conductor 222 to wire L In order to obtain a reduced heat output for the wash and wear cycle of operation, the heater element 214 of thermostat 212 is connected across wires L N through a circuit including conductor 180, door switch 182, cancel switch 192, start. switch 196, a conductor 224, a relay controlled switch 226, a conductor 227 to a switch 228 in the switch bank 185 positioned closed by pressing the wash and wear button 176. The circuit from switch 228 passes through a resistance 229 and a conductor 230 including the heater 214 thence to wire N.

For heating during delicate cycle of operation, the resistance 229 is taken out of the thermostat heater energization circuit by opening switch 228 and closing a switch 232 that is connected by a conductor 234 to conductor 227 and by a conductor 236 to conductor 230 and wire N.

The motor control circuit 188 is connected to wire L through conductor 180, door switch 182, through the start switch 196, conductor 224, relay operated switch 226, a conductor 238 which is connected across a centrifugal switch 240 through the start winding 242 or through a main winding 244 of the fan and drum motor 80, thence through a conductor 246 to wire N.

The control circuit 190 is a suitable electronic system of the type sold by Texas Instruments as a Klixon dryness control wherein suitable solid state electric components are included to control the energization of a relay coil 248 that, when energized, maintains the relay switches 206, 226 closed to complete the heater circuit 186 and the motor energization circuit 188. Additionally, the relay coil 248, when energized, controls a relay switch 250 to complete a holding circuit for the control circuit 190 from wire L through conductor 180, the door switch 182, conductor 184, switch 192 thence through a conductor 252 through switch 250 to conductor 198.

The control circuit of FIGURE 6 also includes an alarm circuit including a conductor 258 connected to a coil 260 of a buzzer alarm 261 which, in turn, is connected to a conductor 262 through the centrifugal switch 240 of the motor 244 when it is running, back to the conductor 238. When the motor stops, the switch 248 is positioned to sound the alarm. Bypassing the coil 268 is a single-pole, single-throw bimetallic operated switch 26 1 serving as a cool-off thermostat whereby the fan motor 80 will continue to operate following heater tie-energization until clothes are cool enough to touch.

The control circuit for controlling the relay switches 206, 226, 250 is operated as follows. When the door switch 182 is closed and the start button 196 is pressed, the circuit 190 is energized from wire L through conductor 180, the door switch 182, conductor 184, the switch 192, conductor 194, thence through switch 196 and through conductor 198 to apply voltage across terminals T T of the control circuit 190. Current thereby passes through a diode 265 and a conductor 266 through the relay coil 248 thence through a conductor 268 and a resistor 270 to excite the gate of a silicon controlled rectified 272 whereby the controlled rectifier conducts from an input line 274 to an output conductor 276 connected to terminal T and thence to wire N through a conductor 278. The energization of the relay coil 248 closes the switches 206, 226, 250 for locking the control circuit 190 for continuous operation and also to complete both the motor and dryer heater circuits 186, 188.

Current also flows through a diode 280 and a resistor 282 across a potentiometer 284 including a movable contact operatively positioned by rotation of the cycle control knob 166 on the control panel 18 thence through a resistance element 286 to charge a capacitor 288 which is connected by a conductor 290 having a resistor 292 therein to ground. As the charge of the capacitor 288 increases, the voltage thereacross causes a neon bulb 294 that is connected by a conductor 296 having a resistor 298 therein to apply a base voltage to a transistor 300. When the transistor 300 conducts, the gate current on the controlled rectifier 272 is by-passed to ground by the transistor 300 through a conductor 301, conductor 276 and conductor 290 to shut off the controlled rectifier 272 whereby the relay coil 248 is de-energized to open the heater circuit 186, the motor circuit 188 and the control circuit 190. A resistor 302 of large magnitude in a conductor 303 shorts out the capacitor 288 through the relay coil 248 when the control is turned off.

The time required for the capacitor charge is dependent upon a series resistant network 304 which is controlled by the potentiometer 284 and the action of the sensor unit 86 within the tumbling drum. More particularly, the series resistant circuit 302 includes a conductor 305 in the control circuit 190 that is serially connected to the resistance of the potentiometer 284. Current flow from the potentiometer 284 to the capacitor 288is, in part,

passed through the conductor 305 of the circuit 304 and thence through the conductor 158 connected to the conductor discs electrically connected to the stud 114 of the sensor 86 through the point contact 160, the spring conductor 150 and the terminal 144, as best seen in FIG- URE 2. The current flow through the series resistant circuit 304 occurs during the drying cycle of operation and is produced by damp clothing in the tumbling drum contacting the nose 100 of the sensor 86 in a manner to bridge the adjacently located insulated conductor discs. When the clothes are relatively wet, the bridging action thereof will cause current to flow from the conductor discs connected to the stud element 114 across the insulating discs thence through the conductor discs connected to the stud element 110 to ground through the terminal 134, the screw 98, the plate 136, shaft 24 and universal bearing 22 to drum ground 140 to the bulkhead 20.

In accordance with certain of the principles of the present invention, the nose probe 100 is constructed and arranged to produce a continuously random contact of the tumbled damp clothes to selectively bleed current from the control circuit 190 to prevent the capacitor 288 from charging so as to de-energize the relay coil 248. In addition to being located in an out-of-the-way location within the interior of the tumbling drum, the sensor unit 86, by virtue of the comically-shaped base portion 88 thereon, and the stepped configuration of the nose 100, will continually act to force the occasional damp articles contacting the conductive discs thereon away from the sensor unit 86 whereby there is an absence of tangling of articles on the sensor unit 86 that might cause the serial resistance circuit 302 to be highly conductive so as to destroy the effectiveness of the control circuit 190.

Furthermore, the location of the sensor 86 in the tumbling drum results in only an occasional contact of the damp clothes therein whereby the bleeding of current from the capacitor 288 is more closely correlated to the degree of dampness of the clothes whereby the control circuit 190 is operative to produce a very close control of the final degree of dryness of clothes when the drying cycle of operation is terminated by the control circuit 190.

The final degree of dryness is determined by the setting of the potentiometer 284 by the control knob 166 and by virtue of the only occasional contact of the sensor 86 with damp clothes, the final dryness can be varied very closely from a maximum of approximately 35% moisture to bone dry depending upon user preference.

A further feature of the location of the sensor 86 in the tumbling drum is that as clothes are moved into contact with the sensor 86, they produce a wiping action against the exposed conductive surfaces thereon that serves to wipe various sizing materials therefrom that are found in many fabrics. Furthermore, the wiping action of the clothes contacting the conductive surfaces on the sensor 86 cleans the surface of any accumulated lint or the like thereon that might reduce the effectiveness of the sensor 86 as a component of the control system.

A further feature of the sensor 86 is found in the provision of the step-wise configuration of the conductor and insulating groups 102, 104, 106. By virtue of the stepwise configuration, the conductor disc 128 of the disc group 102 and its like counterpart in the disc group 104 have a large axially exposed annular conductive surface thereon. These exposed discs surfaces have the same polarity so that when wet clothing bridges them there is no tendency to unduly discharge the capacitor 288. However, the relatively large exposed surface is able to complete a bridge between adjacent conductive discs of an opposite polarity to improve the clothes sensing ability of the sensor 86, notwithstanding its small total surface area.

When the sensor eventually contacts clothes having a dampness as preselected by the control knob 166, the capacitor 288 is charged sufiiciently to de-energ-ize the relay 248 to terminate the heating cycle of operation. Furthermore, the control circuit 190 is de-energized. The motor circuit 188 is maintained energized for a predetermined cool off period through a circuit from wire L through conductor 180, switch 182, conductor 184, switch 192, conductor 194, start switch 196, thence through conductor 224, conductor 258, cool-ofi thermostat 264, conductor 262, switch 240 thence through the main motor winding 244 and conductor 246- back to the wire N. The tumbling drum 26 is rotated by the motor through a cool-off period determined by the cool-off thermostat 264 that eventually opens when the articles are cooled to a predetermined degree to cause the coil 260 to be energized to sound an alarm indicating the end of the drying cycle.

Another feature of the present invention is that the control circuit in FIGURE 5 is operative during a no-heat cycle of operation to include the control circuit and the motor circuit 188 operatively energized whereby the control circuit 190 can be utilized to terminate drum rotation when articles have been dried to a predetermined state by ambient air passing through the tumbling drum interior. More particularly, the no-heat cycle includes placing articles of clothing inside the tumbling drum, then closing the door to close the door switch 182. The noheat and start buttons 170, 168 are then pressed to close switch 196 so that the control circuit 190 is energized, as discussed above, to close the relay switches 206, 250, 226. The switch 200 is maintained open so that the heater 54 is de-energized when the no-heat button is pushed. During the no-heat cycle, the motor 80 is energized from wire L through conductor 180, door switch 182, conductor 184, switch 192, conductor 194, switch 196, conductor 224, switch 226, conductor 238 thence through the main motor winding 244 and conductor 246 to wire N. When the damp clothes reach a predetermined degree of dryness, the sensor 86 will allow the capacitor 288 to be charged to cause the relay 248 to be deenergized to open switch 226 to terminate the no-heat cycle of operation as previously discussed.

While the embodiment of the present invention as here in disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A sensor unit including a comically-shaped base por tion having a large diameter end and a small diameter end, a first plurality of conductor discs on said small diameter end of said base portion, means for electrically insulating each of said first plurality of conductor discs one from the other, a second plurality of conductor discs aligned colinearly with said first plurality of conductor discs, said second plurality of conductor discs having an outside diameter smaller than that of said first discs, means for electrically insulating said second plurality of conductor discs one from the other and from said first plurality of discs, first terminal means on said base portion electrically connected to selected ones of said first and second plurality of conductor discs, second terminal means on said conical base electrically connected to selected other of said first and second plurality of conductor discs, said first plurality of conductor discs adapted to be electrically connected to one another across said insulat ing means to produce a first current path across said first and second terminal means, said second plurality of c0nductor discs adapted to be electrically connected to one another across said insulating means to produce a second current path between said first and second terminal means.

2. In the combination of claim 1, said first and second pluralities of conductor discs being connected to said small diameter of said base portion by connector means forming part of said first and second terminal means.

3. In a domestic clothes dryer, the combination of, a rotatable tumbling drum having a rear wall, a sensor unit on said rear wall located interiorly of said drum including a conically-s'haped base portion having a large diameter end and a small diameter end, first plurality of conductor discs on said small diameter end of said base portion, means for electrically insulating each of said first plurality of conductor discs, a second plurality of conductor discs aligned colinearly with said first plurality of conductor discs, said second plurality of conductor discs having a smaller outside diameter, means for electrically insulating said second plurality of conductor discs one from the other and from said first plurality of discs, first terminal means on said base portion electrically connected to selected ones of said first and second plurality of conductor discs, second terminal means on said conical base electrically connected to selected other of said first and second pluralities of conductor discs, said first plurality of conductor discs adapted to be electrically connected to one another across said insulating means to produce a first current path across said first and second terminal means, said second plurality of conductor discs adapted to be electrically connected to one another across said insulating means to produce a second current path between said first and second terminal means.

4. In a clothes dryer unit, the combination of, a rotatable tumbling drum having a rear Wall, a sensor unit adjacent the center of said rear wall including a base having a large diameter end secured to said rear wall and a conical surface thereon directed inwardly of the interior of said drum, a nose portion secured to said base and located thereby interiorly of said drum, said nose portion including conductive means thereon forming an interrupted current path directly exposed to the interior of said drum, said conductive means adapted to be connected to a dryer control circuit responsive to the moisture in articles tumbled Within said drum, said conductive means on said nose portion randomly contacting articles being tumbled Within said drum to complete said interrupted current path through the tumbled articles for conditioning the control circuit for controlling the operation of said tumbling drum, said conical surface of said sensor base defining an inclined surface for directing articles away from said rear wall and downwardly and across said sensor unit nose portion for wiping foreign matter from said nose portion and said conductive means thereby to maintain said interrupted current path.

5. In a domestic clothes dryer, the combination of, a rotatable tumbling drum having a rear wall, a sensor unit located centrally of said rear wall including a nose portion located interiorly of said drum, said nose portion including first and second electrically conductive discs of a first predetermined outer diameter, an insulator disc between said first and second electrically conductive discs for electrically insulating them one from the other, said insulator disc having an outer diameter greater than that of said first and second conductor discs, first and second terminal means electrically connected respectively to said first and second electrically conductive discs, said terminal means adapted to be connected to dryer control means responsive to the electrical resistivity of articles being tumbled in said drum, said sensor unit nose portion randomly contacting wet articles in said drum whereby said first and second electrically conductive discs are electrically connected through the Wet articles across said insulator disc to condition the control means of the dryer to control the operation thereof in response to the moisture in the tumbled articles, said sensor unit including a conicallyshaped surface having a large diameter end secured to said rear drum Wall and a small diameter end secured to said nose portion for locating said nose portion interiorly of said drum to be randomly contacted by articles as they tumble through the drum interior, said conicallyshaped surface converging toward said nose portion to define an inclined surface across which tumbled articles will slide against and across said nose portion for wiping foreign matter off said nose portion.

6. In a domestic clothes dryer, the combination of, a rotatably tumbling drum having a rear Wall, a sensor unit located centrally of said rear wall including a nose portion located interiorly of said drum, said nose portion including first and second electrically conductive discs of a first predetermined outer diameter, an insulator disc between said first and second electrically conductive discs for electrically insulating them one from the other, said insulator disc having an outer diameter greater than that of said first and second electrically conductive discs, first and second terminal means electrically connected respec tively to said first and second electrically conductive discs, said terminal means adapted to be connected to dryer control means responsive to the electrical resistivity of articles being tumbled in said drum, said sensor unit nose portion randomly contacting wet articles in said drum whereby said first and second electrically conductive discs are electrically connected through the wet articles across said insulator disc to condition the control means of the dryer to control the operation thereof in response to the moisture in the tumbled articles, third and fourth electrically conductive discs on said nose portion having an outer diameter less than that of said first and second electrically conductive discs, said third and fourth electrically conductive discs being electrically connected respectively to said first and second terrminal means, insulator discs on said nose portion for electrically insulating said third and fourth conductive discs one from the other and for electrically insulating one of said third and fourth conductive discs from one of said first and second conductive discs, said insulator discs having an outer diameter less than said first and second conductive discs and greater than the outer diameter of said third and fourth conductive discs, said third and fourth conductive discs contacting wet clothes to complete an electrical path therebetween for further conditioning the dryer control unit, said first, second, third and fourth conductive discs together providing a stepped outer surface on said nose portion for reducing tangling of tumbled articles thereon during rotation of said tumbling drum.

References Cited UNITED STATES PATENTS 2,991,641 7/1961 Woodling 34-45 X 3,059,203 10/ 1962 Hetrick 34-45 3,122,426 2/1964 Horecky 34-45 3,186,105 6/1965 Nye et al. 34-45 FREDERICK L. MATTESON, 111., Primary Examiner. JOHN J. OAMBY, Examiner. 

1. A SENSOR UNIT INCLUDING A CONICALLY-SHAPED BASE PORTION HAVING A LARGE DIAMETER END AND A SMALL DIAMETER END, A FIRST PLURALITY OF CONDUCTOR DISCS ON SAID SMALL DIAMETER END OF SAID BASE PORTION, MEANS FOR ELECTRICALLY INSULATING EACH OF SAID FIRST PLURALITY OF CONDUCTORS DISCS ONE FROM THE OTHER, A SECOND PLURALITY OF CONDUCTOR DISCS ALIGNED COLINEARLY WITH SAID FIRST PLURALITY OF CONDUCTOR DISCS, SAID SECOND PLURALITY OF CONDUTOR DISCS HAVING AN OUTSIDE DIAMETER SMALLER THAN THAT OF SAID FIRST DISCS, MEANS FOR ELECTRICALLY INSULATING SAID SECOND PLURALITY OF CONDUCTOR DISCS ONE FROM THE OTHER AND FROM SAID FIRST PLURALITY OF DISCS, FIRST TERMINAL MEANS ON SAID BASE PORTION ELECTRICALLY CONNECTED TO SELECTED ONES OF SAID FIRST AND SECOND PLURALITY OF CONDUCTOR DISCS, SECOND TERMINAL MEANS ON SAID CONICAL BASE ELECTRICALLY CONNECTED TO SELECTED OTHER OF SAID FIRST AND SECOND PLURALITY OF CONDUCTOR DISCS, SAID FIRST PLURALITY OF CONDUCTOR DISCS ADAPTED TO BE ELECTRICALLY CONNECTED TO ONE ANOTHER ACROSS SAID INSULATING MEANS TO PRODUCE A FIRST CURRENT PATH ACROSS SAID FIRST AND SECOND TERMINAL MEANS, SAID SECOND PLURALITY OF CONDUCTOR DISCS ADAPTED TO BE ELECTRICALLY CONNECTED TO ONE ANOTHER ACROSS SAID INSULATING MEANS TO PRODUCE A SECOND CURRENT PATH BETWEEN SAID FIRST AND SECOND TERMINAL MEANS. 